48 MIND IN EVOLUTION CHAP. 



the sensory surroundings. The latter kind is the typical 

 reflex, and is illustrated in the examples drawn above from 

 the respiratory mechanism. It is in such cases that the 

 reflex act especially impresses us as mechanical. But we are 

 not to regard all reflex actions as of this type. In all higher 

 organisms the reflex is the act of a part rather than the 

 whole of the bodily structure, but it is an act dependent in 

 very varying degrees upon the condition of the whole. If 

 there are some reflexes that proceed with the fixity and 

 sureness of fate, there are others that may be inhibited by 

 a counter stimulus or by a reaction of the whole organism, 

 which we call an effort of will. Such an interaction clearly 

 brings the reflex into closer relation with the condition of 

 the organism as a whole. And this process is carried a 

 step farther where we find reflexes that are not set in motion 

 at all unless the general bodily condition is suitable. Thus 

 " the babe that has had enough does not suck." 1 To put 

 it generally, in addition to the stimulus and the permanent 

 structure there must be a general condition of excitability, 

 or susceptibility to the specific excitement, and this con- 

 dition will depend very much on the requirements of the 

 organism. We here get adjustment to needs again at a 

 higher remove. If the condition of the organism is such 

 that a reaction would be beneficial, then normally the state 

 of excitability is present, and the animal is ready to react 

 as soon as the stimulus appears. The dog's stomach being 

 empty it is good for him to eat, and he is accordingly 

 hungry (ready to be excited by food), and therefore pounces 

 on the bone when he sees it. Conversely the sated dog 

 either buries the bone or neglects it. All this goes to show 

 that the reflex machinery is a part of the whole organism, 

 and may be very dependent for its working on the condi- 

 tion of the remainder. Reflexes vary from the extreme 

 of independence to a comparatively close connection with 

 the general state of the organism. All alike are mechanical 

 in the sense in which mechanism is opposed to purpose. 

 Only the former are mechanical in the sense in which the 

 rigidity of a machine is contrasted with the adaptability of 

 an organism. 



1 Preyer, I. p. 152. 



